I personally could exercise relatively normally until about 16ish weeks and then I could feel some shifting around my hips and switched to lower impact exercise.

Exercise in pregnancy depends on the RPE (rate of perceived exertion). You should be at about 70% RPE in the first two trimesters and down to 50% RPE in the third trimester.

FWIW I rucked with 30 pounds until 26 weeks pregnant and lifted over 100 pounds up until I went into labor because that was within the appropriate RPE for me.

If you want to learn more about exercising in pregnancy, I’d also there are resources on pelvic floor, diaphragmatic breathing, reducing intrabdominal pressure, etc.

If you're sure you can maintain good posture while using it... then I guess it's fine. Don't forget your joints get looser and more prone to injury. Maybe not in the 3rd trimester, though.

Wondering if it’s ok to continue using my weighted vest during the first trimester, and possibly the second trimester? I only carry around 12 pounds of weights but would decrease to maybe 6 during the second trimester (if it’s ok). I’m in good physical shape and exercise regularly and want to find a substitute for jogging since it makes me a bit nauseous.